Two stereoisomers of C-unalkylated calix[4]resorcinarene and the conformation change

SummaryC-unalkylated calix[4]resorcinarene octamethyl ether was prepared by the HCl-catalyzed condensation of 1,3-dimethoxybenzene with paraformaldehyde in 2-ethoxyethanol. The conformation of the C-unalkylated calix[4]resorcinarene was preferentially chair-like when the large amount of conc.HCl was used. The conformation changed from a chair-like to a boat-like isomer by heating in the temperature range from 240 to 250 °C in bulk.